Method of joining strip



Jan. 5, 1965 J. E. NIELSEN 3,163,931

METHOD OF JOINING STRIP Filed July 28. 1960 FIE'B Y INVENTOR.

JOHN E. N/E'LS'N BYM W H/S 4 TTOP/VEYS United States Patent 3,163,931 METHGD 0F IOINING STRIP John E. Nielsen, Downers Grove, Ill assignor to Reynolds Metals Company, Richmond, Va, a corporation of. Delaware Filed duly 28, 196i Ser. No. 45,883

Claims. (Ci. 295tl?) This invention relates to a method for joining sheets. More particularly this invention relates to a method for joining superimposed sheet members wherein portions of the sheet members are deformed to serve as fasteners.

Strips of sheet materials may often be joined by staples or other simple fastening devices. However, in the nonferrous metallurgy arts, for example, where contaminates such as staples cannot be tolerated, no completely satisfactory system has heretofore been developed for joining sheet materials. The joints formed between the strips usually must be quite strong and, where the strips are joined during rolling or other continuous processes, the

. joints must be rapidly made. Several methods have been devised whereby portions of the strips of sheet material are superimposed and segments of the superimposed portions are then partially punched to deform the material in one direction. The deformed portion is then coined or swaged so as to overlie the rest of the sheet material. Subsequently the deformed portion is flattened to lie in substantially the same plane as the superimposed sheets with the coined or swaged pants overlapping the rest of the sheets. At times, the coining or swaging operation is done concurrently with the flattening operation with complicated spring dies and punches. Up to the present, it has been necessary severely deform the superimposed sheets as a first step and then to severely coin or swage the deformed portion. Accordingly, the prior methods, generally speaking, have been applicable only when joining sheets having a fairly narrow range of thicknesses and comparatively high ductility.

An object of this invention is to provide a method for joining strips of sheet material by controlled steps of deforming the sheet material which may be applicable to various thicknesses of sheet material having various degrees of ductility.

For a better understanding of this invention and its other objects, advantages and details, reference is now made to the present preferred embodiment of the invention which is shown for purposes of illustration only in the accompanying drawing. In the drawing:

FIGURE 1 is a partial perspective view of a pair of sheet members which are to be joined in accordance with the method provided by this invention.

FIGURE 2 is an end View of the sheet members of FIG- URE 1 illustrating diagrammatically the manner in which the sheets are to be initially deformed.

FIGURE 3 is a view similar to FIGURE 2 illustrating the manner in which the punches in FIGURE 2 have completed the initial deformation of the sheets.

FIGURE 4 is a partial perspective view of the sheets of FIGURE 1 after initial deformation.

FIGURE 5 is a diagrammatic perspective view showing a pair of die members used in the second deforming or flattening stage in accordance with the method of this invention.

FIGURES 6, 7 and 8 illustrate diagrammatically the manner in which the die members of FIGURE Sfare used to flatten the deformed portions of the sheets.

FIGURE 9 is a partial perspective view of the sheets of FIGURE 1 as they'appear after being joined in accordance with the system described hereinafter.

FIGURE 10 is a sectional view of a pair of fastened sheets taken along lines 1tllll of FIGURE 9.

Patented Jan. 5, .1965

In accordance with this invention, a pair of sheets such as members It and 12, are first partially superimposed at their ends, as shown in FIGURE 1. The sheets 10 and '12 may be non-ferrous metals, such as aluminum, but the invention disclosed herein could be used in joining-other types of sheet materials. The superimposed portions of the sheets It and 12 are then placed between a row of opposed, interdigitating punches 14 and 16 asshown in FIGURE 2. The purpose of the punches 14 and 16 is to form a laterally extending row of alternate upwardly and downwardly directed hollow protuberances by displacing adjoining portions of the two sheets in opposite directions into a sinusoidal wave-like pattern. Considering the portions of the sheets which form the upwardly directed protuberances 20 in FIGURE 3, it is apparent that the. punches 16 displace superimposed portions of each sheet upwardly so that the bottom face of the lower sheet 12 extends above the plane of the top face of the upper sheet Ill. Since the punches 14 interdigitate with the punches 16, the immediately adjacent portions of the sheets are deformed into oppositely directed protuberances 22. Each protuberance 20, 22 is separated from the adjoining protuberances by a longitudinal shear line 24 cut into the sheet members by the adjacent edges of the punches 14 and 16. While the material between pairs of shear lines 24 is stretched to form the protuberances, the material does not split or crack except along the shear lines 24 because the punches 14, 16 have comparatively smooth contours.

The shape of the protuberances 20, 22 is of considerable importance. Each protuberance has a central arch '26 extending laterally of the sheets and semi-circular side panels 23. The panels 28, which are integral with the sheet members, extend inwardly of the protubera'nces so that the arches 26 are narrowest at their crests. The sloping sides of the arches 2-6 extend at an approximately 30 angle from the plane of the sheets and terminate in sheared marginal edges 30. The edges 30 of the protuberances 29 extend above the top surface of sheet 10 while the edges 30 of the protuberances 22 extend below the bottom surface of the sheet 12. The sloping sides of the arches 26 are advantageous in that the degree of deformation of the sheets is minimized; Also the sheets may be securely joined without the necessity of a coining or swaging operation upon flattening as will be further discussed below. i

It is thus seen that a lateral row or stitch of identical protuberances 20, 22 extending alternately in opposite directions between a plurality of parallel shear lines 24 is formed in the superimposed sheets. Only one more step is required to join the sheet members,namely that of flattening the protuberances to form a .plurality of adjoining fastening devices.

The protuberancesare flattened in two stages, using a pair of finger dies 32, 34 shown most clearly in FIGURE 5. Gne half of the working surface of each die 32, 34 r is planar while the other half is provided with a row of coplanar fingers 36 extending along one edge thereof, each finger 36 beingseparated by depressions 38. The two dies 32, 34 are arranged such that the fingers 36 of die 34 lie beneath the planar surface of die 32 while the planar surface of die 34 lies beneath the fingers of die 34. As diagrammatically illustrated in FIGURES 6, 7

and 8, the finger dies 32, 34 are used to consecutively fiatten first the top row of protuberances. 20 and then the bottom row of protuberances 22. Initially the sheets 10 and 12 with the protuberances 2t 22 formed therein are placed between the dies 32, 34 as shown in FIGURE 6.

The fingers 36 of die 54 extend under the protuberances 20 to support the sheets 10 and 12 beside the protuberances while the depressions 38 are sufliciently wide to re ceive the protuberances 22. As shown in FIGURE 7,

. out of the plane of the sheet members.

the die 32 .is lowered to flatten the protuberances 29. The superimposed sheets are then shifted to occupy the position shown in FIGURE 8 wherein the flattened protuberances extend within the depressions 33 of die 32 while the protuberances 22 are flattened by being squeezed between the flat surface of die 34 and the fingers of the die 32. I

The final result of the flattening operations is shown in FIGURES 9 and 10. Each of the protuberances 29 have been flattened to form generallyrectangular fastening elements 129 whileeach of the protuberances 22 have been flattened to form generally rectangular fastening elements 122. As the protuberances 20 are flattened, the

sheared edges 30 thereof expand outwardly to form arcuate end flanges 124 extending beyond the adjacent shear lines. Afterwards, upon flattening of the protuberances 22, the sheared edges thereof formarcuate end flanges 126 which extend beyond the original shear lines 7 to overlap the adjacent fastening elements 129. Each of the fastening elements 129, 122 then, comprises a rectangular portion and a pair of arcuate end flanges projecting from opposite sides of the rectangular portion. The overlap is producted by two factors. Since the material forming the protuberances 20, 22 stretches upon initial deformation of the sheet members, the sheared edges 30 tend to expand outwardly causing a portion of the overlap. The overlap is increased since the edges 30 also move upwardly and outwardly as the sloping sides of the arches 26 are flattened. Generally it has been found that the increased overlap due to upward and outward movement of the sheared edges is equal to about half the thickness of the sheets 10 and 32' Thus, a separate coining of swaging operation is unnecessary because of the special construction of the punches and the corresponding shape of the protuberances 2t), 22.

The comments so farregarding the fastening elements 120 and 122 have been directed to the fact that the sheared edges of each protuberance expand laterally so edges of the panels 28 will resist flattening more than the arches 26. The sloping sides of the arches 26, then,-

will rotate and expand outwardly more easily. Also, initially the crest of each proturberance will buckle slightly before the semi-circular edges of the panels 28 flatten, thus causing a very slight oval depression centrally of each flattened protuberance. Since the semi-circular edges of the sides 28 are comparatively sharp and since an oval depression is formed centrally of the fiattened proturberances, the fastening elements 122 and will be slightly corrugated, as indicated by lines in FIGURE 9. The effect of the slight corrugation is to stiffen the fastening elements.

The fastening elements 12il, 122 then are quite advantageous in that they provide a strong joint both laterally and longitudinally of the sheet members. The overlap between adjoining fastening members is surhcient to provide a strong, continuous joint. If it is desired to have members, the sloping sides of adjacent protuberances will buckle, causing some of the adjoining sheared edges to partially abut. Of course, in the event. the adjoining sheared edges do abut, they cannot overlap, so the resulting joint is thereby weakened. For this reason it hasbeen found expedient to flatten only the upwardly or downwardly directed protuberances simultaneously and otherwise support the opposite side of the sheets during the flattening operations.

It is thus seen that a pair of sheet members may be rapidly and tightly joined following the simple steps speci fied above. Prior to this invention, it has been thought necessary to separately coin or swage the edges of the deformed material either as a completely separate step or during the flatteningoperation by means of complicated spring punches or the like. However, with this invention, no separate coining or swaging operation is required to form the fastening elements 128, 122 due to the shape of the displaced protuberances formed in the sheet members. As noted earlierjthe initial punching operation does not severely deform the sheet members. Accordingly, the steps described above may be applied to various thicknesses of comparatively brittle metals as well as various thicknesses of metals having a high ductility. It

has also been found that the pressure required to produce the'protuberances is comparatively small so that it is possible to punch an entire row of protuberances simultaneously. Therefore, the above steps may be performed rapidly with relatively simple equipment.

While I have illustrated and described a present preferred embodiment of the invention, it will be recognized that the invention may be otherwise variously embodied and practiced within the scope of the following claims.

Having thus described my invention, 1 claim:

1. In a method for joining sheet members composed of metal or like material, the steps of displacing adjoining superimposed portions of the members inwardly from the ends thereof to form adjoining, oppositely directedhollow protuberances; simultaneously shearing the members between said protuberances to provide a shear line defining the common marginal edges thereof and stretching the displaced portions in a direction perpendicular to said shear line, the adjoining sides of said protuberances extending angularly toward the plane of the sheet members from opposite sides thereof in substantially tangential relation to each other and terminating in the sheared edges; and flattening said protuberances whereby said edges expand outwardly in overlapping relationship.

2. A method for joining sheet members composed of metal or like material, comprising the steps of displacing adjoining, superimposed portions of the members inwardly from the ends thereof to form a row of hollow protuberances extending alternately from opposite sides of either the top or the bottom of the joints coplanar with the top or bottom sheet respectively, it is possible to manipulate the finger dies 32, 34 so that only one row of fastening elements, that is either elements 120 or 122, extend Usually, however, this is unnecessary. 7

It will be obvious to those skilled in the art that the protuberances 20, 22 could be flattened in other ways. For example, the superimposed sheets could be placed between fiat die faces which are actuated to simultaneously flatten all of the protuberances. In practice, however, the resulting joint is not always satisfactory, In the absence of a support, such as that provided by the finger dies 32, 34 for the sheet members in the area of the protuberance being flattened, the protuberance will buckle in an irregular wave-like fashion. When adjacent protuberances are flattened simultaneously by the flat faces of opposed die the sheet members, simultaneously shearing the members at the juncture between adjacent protuberances and stretching each of the displaced portions intermediate the sheared edges; each of said protuberances having sloping sides terminating in the sheared edges; and flattening the protuberances whereby the edges of adjoining sloping.

sides thereof expand outwardly to form a row of fastening elements having overlapping portions.

3. The method of claim 2 in which the protuberances extending in one direction are flattened prior the fiattening of the protuberances extending in the opposite directions.

4. A method for joining a pair of sheet members composed of metal or like material, comprising the steps of superimposing the ends of said members, punching the members inwardly from the ends thereof to form a lateral row of alternately oppositely directed adjoining protuberances by means of a pair of rows of interdigitating punches extending laterally of the members, each adjacent pair of punches having cooperative shearing edges,

and advancing the punches so as to shear the members along the juncture between adjacent protuberances, thereby providing a longitudinal shear line separating said protuberances at their common marginal edges, each of said protuberances including a central arch having sloping sides terminating in said marginal edges; and flattening the protuberanees whereupon the edges of adjoining slop 5 ing sides expand laterally in overlapping relationship.

5. The method of claim 4 in which the protuberances extending in one direction are flattened before the protuberances extending in the opposite directions are flat tened, and Which further includes the steps of supporting one side of the sheet members adjacent the protuberances 6 while the protuberances on the other side are being flattened.

References Cited in the file of this patent UNITED STATES PATENTS 430,000 Clark et a1 June 10, 1890 493,791 Schurig Mar. 21, 1893 512,021 Gould Jan. 2, 1894 1,618,279 Fedders Feb. 22, 1927 2,254,558 Williams Sept. 2, 1941 2,688,890 Williams Sept. 14, 1954 2,912,075 Pfistershammer Nov. 10, 1959 

1. IN A METHOD FOR JOINING SHEET MEMBERS COMPOSED OF METAL OR LIKE MATERIAL, THE STEPS OF DISPLACING ADJOINING SUPPERIMPOSED PORTIONS OF THE MEMBERS INWARDLY FROM THE ENDS THEREOF TO FORM ADJOINING, OPPOSITELY DIRECTED HOLLOW PROTUBERANCES; SIMULTANEOUSLY SHEARING THE MEMBERS BETWEEN SAID PROTUBERANCES TO PROVIDE A SHEAR LINE DEFINING THE COMMON MARGINAL EDGES THEREOF AND STRETCHING THE DISPLACED PORTION IN A DIRECTION PERPENDICULAR TO 